The objective of this research is to provide the first rapid and reliable assay for detecting endotoxin (lipopolysaccharides form gram-negative bacteria) in whole blood samples. The assay employs a very sensitive agglutination inhibition methodology. The red blood cells present in normal, endotoxin negative, whole blood samples agglutinate in the test within 60 seconds. Samples from patients suffering from endotoxin in the blood will show inhibition of erythroagglutination. In preliminary studies, the assay has been shown to correlate with clinical suspicion of endotoxemia in horses hospitalized with symptomatic colic. The specific aim of the research is to refine the assay using equine colic as a model system for aseptic endotoxemia. Results obtained with the agglutination inhibition assay will be compared with Limulus amoebocyte lysate (LAL) test results and clinical findings to determine specificity and sensitivity. The assay will be converted to determine and quantitate endotoxin in human blood. The availability of an endotoxin test will allow for improved diagnosis and therapy of people suffering septicemia, pneumonia, and other gram-negative bacterial infections. Use of this assay may also prove to be valuable in protecting the supply of donated blood and blood products from contamination by endotoxin.